Conventional methods of rock breakage, including drilling-and-loading-and blasting and crushing techniques have several disadvantages.
The drill-and-load-and-blast technique has the disadvantage of noise, gases, dust and flying debris, which means that both men and machines must be evacuated from the working area. Crushing techniques require large forces to crush the rock and the tool wear is significant.
During the last decade serious attention has been given to replacing the drill and blast technique for tunneling, mining and similar operations. One alternative technique involves the use of high velocity jets of water or other liquid to fracture the rock or ore body and numerous devices intended to produce pulsed or intermittent liquid jets of sufficiently high velocity to fracture even the hardest rock have been suggested. As yet, however, jet cutting techniques are still unable to compete with the traditional methods of rock breakage such as drill and blast in terms of advance rate, energy consumption or overall cost. Moreover serious technical problems such as the fatigue of parts subjected to pressures as high as 10 or 20 kbar and excessive operational noise remain.
A second, and even older technique for fracturing the rock and for saturating soft rock formations such as coal with water for dust suppression involves drilling a hole in the rock and thereafter pressurizing the hole with water either statically or dynamically.
These methods are inapplicable to hard rock formations because of the restriction in working pressure which can be realized or usefully utilized with conventional hydraulic pumps. They are difficult to apply in practice particularly in soft crumbling rock or badly fissured rock in that the bore hole must be effectively sealed around the tube introduced into the hole through which the liquid is pumped. These restrictions in all make the method far less versatile than drill and blast.
In applicant's Swedish patent specification No. 7510559-3 a hydraulic breaking technique is described which makes it possible to break hard compact material such as rock by using an equipment which operates at comparatively low pressures.